The scope of the research was to investigate the impact of drugs on the emergence of criminal careers. To this end, a search was conducted in documents from more than 1200 police enquiries, from which the individuals in the sample were extracted. Once the sample was formed, each of these individuals whose first offences were committed in the years 1985, 1990 and 2005, a cohort of 20 years therefore. These individuals had their criminal trajectories investigated based on criteria of age, education, severity of offences and development or not of a criminal career. The conclusion of the study was that individuals whose first access to the criminal justice system was due to an offence related to illicit drugs tended to develop criminal careers. The age at which the first offence was committed as well as the level of education also had a positive influence on the development of a criminal career. Finally, the study also found that individuals whose crimes were more serious were younger and had lower education levels when they committed their first offence.